Tubular trimmer condenser



May 28, 1957 H. M. wADswoRTH 2,794,159

TUBULAR TRIMMER CONDENSER Filed March 22, 1954 V IN VEN TOR. Mani/(Z 722. wwmvzz WI TNESS:

;zzz:z1.$m "mam T ORNEY United States Patent TUBULAR TRIMIVIER CONDENSER Howard M. Wadsworth, Liverpool, N. Y.

Application March 22, 1954, Serial No. 417,877

3 Claims. (Cl. 317249) The present invention relates to a tubular trimmer condenser for tuning high frequency electronic circuits, and more particularly a tubular condenser having a rotary electrode.

In some electronic circuits it is desirable to incorporate a trimmer condenser which may be rapidly adjusted from maximum to minimum capacity by a half rotation of the rotor but which is mechanically stronger and less subject to deformation, and is more resistant to break-down or corona effects than the rotary plate types of trimmer now available.

It is an object of the present invention to provide a trimmer condenser answering these requirements while performing its function efficiency and in a stable manner.

It is another object to provide such a device which is simple and economical in construction and convenient to install and adjust.

It is another object to provide such a device having means for varying its range of adjustment by longitudinal movement of the rotor, thus rendering it adjustable to various purposes and environments.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is a side elevation, partly broken away and in section of a preferred embodiment of the invention;

Fig. 2 is a section taken substantially on the line 22 of Fig. 1;

Fig. 3 is a section taken substantially on the line 33 of Fig. 1; and

Fig. 4 is a view of the blank from which the inner electrode is formed.

In Fig. 1 of the drawing there is illustrated a cylindrical tube 1 of dielectric material having a semi-cylindrical external coating or sheath 2 of conductive material such as metallic foil suitably aflixed thereto. This sheath forms the outer electrode of the condenser and is electrically connected to a metallic cap 3 provided with a terminal strip 4.

The tube 1 is rigidly mounted on a metallic bushing 5 as by metallizing the exterior of the tube and soldering it to the bushing as indicated at 6. The bushing is arranged to be fixed in a panel 7 as by means of a clamp nut 8.

The interior electrode is formed from the blank illustrated in Fig. 4. This blank comprises a rectangular central portion 9, and rectangular panels 11 and 12 extending from the sides thereof. Semi-circular projections 13 and 14 extend from the ends of the central portion 9, and at least one of these projections is punched out as indicated at 15 to form an arch-shape which leaves a portion 16 of the end of the central panel 9 exposed.

In forming the electrode the side panels 11 and 12 are bent upward along the dotted lines 17 and 18 respec tively and are then curved toward each other to form cylindrical surfaces of slightly larger radius than the interior radius of the dielectric tube 1. The panels are of such length that taken together they form almost a com plete semi-cylinder when introduced into the tube 1 as shown in Figs. 2 and 3. The semi-circular or arch-shaped projections 13, 14 are bent in the opposite direction along the dotted lines 19 and 21 respectively until they occupy positions perpendicular to the central panel 9, and thereby constitute guides or runners adapted to bear on the interior of the dielectric tube 1 and thus maintain the central panel 9 in a substantially diametrical relation with the interior of said tube. For this purpose, the peripheries of the projections 13, 14 are substantially equal in radius to the interior of the tube.

In order to actuate the interior electrode a screw shaft 22 provided with a diametrical slot 23 in its end is inserted through the opening 15 in the runner 14, and pressed on the central panel 9 until the edge 16 thereof bottoms in said slot. The shaft is then permanently attached in any suitable manner as by soldering.

In assembling the trimmer, the cylindrical panels 11, 12 are compressed slightly to permit the electrode to be slid into the tube 1, and then the screw shaft 22 is threaded into the bushing 5 and the assembly of the unit completed by soldering the tube to the bushing at 6.

The capacity of the condenser is varied by rotating the inner electrode to bring the semicylinder formed by the panels 11, 12 more or less into registry with the external Semi-cylindrical electrode 2. The shaft 22 is provided with any suitable means for adjustment such as a screw driver slot 24.

In some installations it is desirable to be able to adjust the maximum capacity of the condenser in order to provide a convenient scale of adjustment. For this purpose, the di-electric tube 1 is made approximately twice as long as the external electrode 2, and the telescopical relation of the inner electrode with the outer electrode may be varied by moving the inner electrode toward or away from the outer electrode by rotation of the screw shaft 22. In this manner the maximum and minimum capacity of the condenser may be adjusted to suit its particular environment.

It will be understood that during each complete revolution of the rotor, the capacity of the condenser will vary from maximum to minimum and back to maximum, but as the rotor is thus threaded into further telescopic relation with the external electrode, the successive maxima will increase until the electrodes are longitudinally coextensive, which provides the peak capacity of the device.

Although but one form of the invention has been shown and described in detail, it will be understood that changes may be made in the design and arrangement of the parts without departing from the spirit of the invention as defined in the claims.

I claim:

1. In a tubular trimmer condenser a hollow cylinder of dielectric material, a part-cylindrical outer electrode fixed on the exterior thereof, an inner sheet metal electrode member slidably journalled in the cylinder comprising a rectangular web portion, a pair of elastic curved panels extending from the longitudinal edges of the web toward each other to form a part-cylindrical inner electrode elastically engaging the interior of the cylinder, a pair of semi-circular arch-shaped guides extending in radial planes from the ends of said web and conforming with and bearing on the interior of the cylinder opposite to the panels of the inner electrode to maintain said web portion centrally located with respect to the bore of the cylinder and thereby cooperate to maintain full surf-ace contact of the panels of the inner electrode with the interior surface of the cylinder and means attached to one end of said web for moving the inner electrode more or less into registry with the outer electrode.

2. A tubular trimmer condenser as set forth in claim registry with the outer electrode to vary the range of 1 in which the means for moving the inner electrode the rotary adjustment of the inner electrode. comprises a bushing fixedly attached to one end of the cylinder, and a shaft threaded axially through the bush- References Cited n h fil f this patent ing, traversing the adjacent arch-shaped guide and rigidly 5 UN E STATES PATENTS attached to the end of the web.

3. A rotatable tubular condenser as set forth in claim gg 1940 sworth Feb. 13, 1951 2 1n whlch the dielectric cylinder 15 substantially twice 2,556,453 Sperry June 12 1951 as long as said electrodes, the outer electrode being 10- cated at one end thereof whereby the inner electrode may 10 FOREIGN PATENTS be moved by the threaded shaft axially into and out of 6 8,228 Great Britain Jan. 3, 1951 

